Cushioned anvil for rock hammers and the like

ABSTRACT

A rock-breaking hammer or drill in which a tool is mounted with freedom for limited longitudinal movement in a tool holder and in which the energy of the hammer head blows is transmitted to the tool through a free striker plate resting on a rubber pad supported on a further plate which is rigid with the tool holder and against which, in operation, an anvil is pressed by the tool.

United States Patent [191 Nancarrow [4 1 Oct. 7, 1975 CUSHIONED ANVIL FOR ROCK HAMMERS AND THE LIKE [75] Inventor: Lawrence Nancarr0w,Tynemouth,

England [73] Assignee: Arrow Construction Equipment Ltd., England [22] Filed: Apr. 15, 1974 [21] Appl. No.: 461,148

[30] Foreign Application Priority Data Apr. 19, 1973 United Kingdom 19037/73 [52] US. Cl 173/131; 299/94 [51] Int. Cl. E21C 37/24 [58] Field of Search 173/131; 299/94 [56] References Cited UNITED STATES PATENTS 1,883,010 10/1932 Sherwood ..l73/131X 1,884,946 10/1932 Wineman 299/94 X 2,184,745 12/1939 Kinneman..... 3,327,516 6/1967 Anderson 173/131 X Primary ExaminerErnest R. Purser Attorney, Agent, or Firm-l ,arson, Taylor & Hinds [57 A ABSTRACT A rock-breaking hammer or drill in which a tool is mounted with freedom for limited longitudinal movement in a tool holder and in which the energy of the hammer head blows is transmitted to the tool through a free striker plate resting on a rubber pad supported on a further plate which is rigid with the tool holder and against which,in operation, an anvil is pressed by the tool.

3 Claims, 2 Drawing Figures US. Patent Oct.7,1975 smetlofz 3,910,357

US. Patent Oct. 7,1975 Sheet 2 of2 3,910,357

FIG 2 I! Fl CUSHIONED ANVIL FOR ROCK HAMMERS AND THE LIKE DESCRIPTION The invention relates to rock-breaking and like hammers and drills of the kind in which a tool holder is repeatedly struck by a reciprocating head so that the tool gives successive blows to the rock or other work.

The shock loadings on such hammers are high and we have found that the energy of the instantaneous blows imparted to the rock by the tool does not appear to have its full effect.

We have discovered that if a resilient pad is interposed between the head and the tool itself a more satisfactory energy utilisation is obtained but, however, that with some constructions severe damage to the tool holder rapidly occurs.

According to the invention a rock-breaking or like hammer or drill, which is of the kind having a head applying successive blows to a tool, has a resilient pad resting on a thick metal plate fixed in the tool holder, a free striker plate supported on the pad to be struck by the head, and the tool is supported below the fixed plate with freedom to move towards and away from it, the energy of the blows being transmitted from the striker plate through the pad and fixed plate to the tool.

Preferably the fixed plate has a gapped ring welded to it to provide a locating wall receiving the resilient pad and striker plate. Moreover there is conveniently an anvil between the fixed plate and the tool.

One construction of rock-breaking hammer according to the invention is illustrated by way of example in the accompanying part-sectional drawings.

In the drawings:

FIG. 1 is an elevation, partly in cross-section, of the hammer, and

FIG. 2 is a view in the direction of arrow 2 on FIG. 1.

The hammer (FIG. 1) comprises a frame 10, schematically indicated, the uprights 11 of which constitute guides for a dropping weight 12 and a tool holder 13. The dropping weight has a head 14 carrying a dolly 15 by which the energy of the dropping weight 12 is applied to the tool holder 13 and thus the tool 16.

The tool holder 13 comprises a main casting of basically H-form whereof the side members 17 have outwardly-facing V-channels 18 (FIG. 2) to engage the uprights 11 and whereof the cross-member 19 carries the blow transmitting parts and the tool 16.

The cross-member 19 has secured to it by bolts 21 a top plate 20, which may be say 1 /2 inches thick, the bolts 21 being locked by set screws 22. The plate has welded to it two semi-circular members 24 defining the walls of a cylindrical well to receive freely a rubber pad 25 and a striker plate 26. The longitudinal edges of the members 24 are spaced apart to leave narrow gaps 27. The pad 25 is for example /2 inch thick and 7 /2 inches in diameter.

A retainer ring 28 is secured to the members 24 by bolts 29 extending into external ribs 24a on the members and coil springs 30 arelocated between the heads of the bolts 29 and the ring. Set screws 31 lock the bolts 29 in position. I

The cross-member 19 has a central stepped-chamber hole receiving an anvil 32 which, when the tool 16 is fully raised, contacts the top plate 20. The tool 16 is prevented from falling from the tool holder by being formed near its upper end with a thick circumferential rib 16a which is received with limited longitudinal clearance in channels 33 in retainers 34 secured by bolts 35 on facings machined in stiffening webs of the main casting.

Lateral webs 36 extend between the members 24 and the top plate 20 to provide attachment points for a chain 37 which can be hooked on to the head 14 so that the tool holder 13 can be raised clear of the work. When operating however the chain hangs freely.

In use of the hammer, the tool 16 is positioned, the chain 37 is dropped to allow the tool 16 to contact the rock and the hammer is allowed to act until it breaks the rock, the energy of the blows struck by the head 14 being transmitted by the dolly 15 to the striker plate 26 and thence through the rubber pad 25, top plate 20 and anvil 32 to the tool 16. Finally the chain 37 is hooked up again and the tool is repositioned for further work.

The action of the pad 25 is to reduce the shock loads transmitted to the hammer as a whole and also tends to extend the period for which the breaking force is exerted on the rock.

The hammer is hydraulically operated but the invention is not limited to such operation.

It will be appreciated that the rubber pad is subjected to heavy stresses and it is therefore desirable carefully to select the form of rubber material employed to prevent its rapid deterioration.

One suitable rubber is a Butadiene-acrylonitrile elastomer sold under the Registered Trade Mark GACO, reference 3.90.

I claim:

1. A rock breaking hammer or drill comprising a frame having a tool holder mounted thereon and a blow-imparting member reciprocable on the frame towards and away from the tool holder, said tool holder having a stepped chamber, an anvil in said chamber, a thick metal plate rigidly secured to the tool holder and closing the chamber, said plate being held in contact with the anvil, a rubber pad supported directly on the thick metal plate and a striker plate supported directly on the rubber pad to be struck by the blow-imparting member, and a rock breaking tool supported by the tool holder with limited freedom lengthwise of the tool to be held in contact with the anvil when the tool rests on the rock which is to be broken.

2. A rock breaking hammer or drill according to claim 1, wherein the thick metal plate has secured thereon a gapped cylindrical wall forming a well in which the rubber pad and striker plate are received.

3. Apparatus as claimed in claim 2 wherein said tool holder is of generally H-shaped sectional configuration as viewed normal to the length of said tool, the upright side members of the H configuration being formed for sliding engagement with upright members comprising said frame, the cross-member of the H configuration having said stepped chamber formed therein, said thick metal plate being rigidly but removably secured to the upper surface of said cross-member, and said tool being removably supported beneath said cross-member.

* l =I =l 

1. A rock breaking hammer or drill comprising a frame having a tool holder mounted thereon and a blow-imparting member reciprocable on the frame towards and away from the tool holder, said tool holder having a stepped chamber, an anvil in said chamber, a thick metal plate rigidly secured to the tool holder and closing the chamber, said plate being held in contact with the anvil, a rubber pad supported directly on the thick metal plate and a striker plate supported directly on the rubber pad to be struck by the blow-imparting member, and a rock breaking tool supported by the tool holder with limited freedom lengthwise of the tool to be held in contact with the anvil when the tool rests on the rock which is to be broken.
 2. A rock breaking hammer or drill according to claim 1, wherein the thick metal plate has secured thereon a gapped cylindrical wall forming a well in which the rubber pad and striker plate are received.
 3. Apparatus as claimed in claim 2 wherein said tool holder is of generally H-shaped sectional configuration as viewed normal to the length of said tool, the upright side members of the H configuration being formed for sliding engagement with upright members comprising said frame, the cross-member of the H configuration having said stepped chamber formed therein, said thick metal plate being rigidly but removably secured to the upper surface of said cross-member, and said tool being removably supported beneath said cross-member. 